The present invention relates to gas generating compositions that are loaded in a gas generating apparatus for inflating an airbag or in a pre-tensioner apparatus for retracting a seat belt, the airbag and the seat belt being mounted on, for example, a vehicle to provide protection for passengers of such vehicles.
Gas generating agents for inflating air bags of the type described above have been known that contain as major components sodium azide and various oxidizing agents. In recent years, however, there is an increasing need for a gas generating composition that is free of sodium azide, because of the strong toxicity of the compound and the difficulties in handling the compound. Also, a gas generating composition is needed that has following advantages: improved stability over time and a proper burn rate; non-production of carbon monoxide or combustion residues; improved handleability and significant gas generation; and low cost. To meet these requirements, significant effort has been made to develop gas generating agents that contain ammonium nitrate as a major component.
Japanese Unexamined Patent Publication No. 11-92265 discloses a gas generating composition containing carbon black or activated carbon and phase-stabilized ammonium nitrate. This composition is advantageous in terms of gas generation and combustion efficiencies and has a high burn rate.
Though the gas generating composition described in the above-mentioned publication is designed in consideration of various combustion-related properties such as the gas generating efficiency and the burn rate, less emphasis has been put on stability over time. Thus, the composition is not suitable with regard to the stability during storage before it is put to use, especially under high temperature conditions.